Layers of lipids in stratum corneum of the skin form a "water barrier" which prevents water loss from the skin. Known classes of stratum corneum lipids include ceramides, free fatty acids, sterols and sterol esters, and phospholipids, with ceramides being a major component.
Although several species of natural ceramides have been identified, these ceramides must be obtained through a lengthy process involving the extraction of ceramides from natural sources. Thus, the availability of natural ceramides is limited and their cost is very high.
Several analogs of natural ceramides, known as pseudoceramides, have been synthesized. Pseudoceramides look similar but are not identical to ceramides. The water retaining function in stratum corneum of pseudoceramides has been described. See for example, J. Soc. Cosmet. Chem., 40, 273-285 (1989). Cosmetic compositions are known which utilize pseudoceramides to control water loss and/or to repair damaged (e.g., dry, flaky, chapped, wrinkled) skin by replacing the skin's natural lipids. See for example, U.S. Pat. Nos. 5,206,020 (Critchley et al.), 5,198,210 (Critchley et al.), 5,175,321 (Ohashi et al.), 4,985,547 (Yano et al.), and 4,778,823 (Kawamata et al.). European Patent Application 556,957 discloses compositions which are said to be particularly effective for prevention or amelioration of skin wrinkling, chapping or ageing, the compositions including (i) a ceramide or a pseudoceramide; (ii) a fatty acid or a fatty alcohol; and (iii) cholesterol or a plant sterol.
Unfortunately, pseudoceramides are still expensive, albeit not as expensive as natural ceramides. The ternary active system referred to in the European Application 556,957 is even more expensive than a single active pseudoceramide-based compositions, due to a relatively high cost of cholesterol. Thus, there is a continuing need for more cost-effective pseudoceramide-containing compositions, i.e., more efficacious and lower cost pseudoceramides and/or more beneficial reduced cost combinations of pseudoceramides with other ingredients.
Accordingly, it is an object of the present invention to provide novel pseudoceramides while avoiding the disadvantages of prior art.
It is another object of the present invention to provide processes of preparing novel pseudoceramides.
It is yet another object of the invention to provide novel pseudoceramides which can be obtained at a relatively low cost.
It is still another object of the invention to provide compositions containing novel pseudoceramides in combination with other beneficial ingredients which compositions are at least as efficacious as conventional pseudoceramide-containing compositions but which can be produced at a lower cost.
These and other objects of the invention will become more apparent from the detailed description and examples that follow.